“Forensic work is a major factor in getting that done. We are re-examining what the police seized 20 years ago.

“The evidence would have been examined to the capabilities the police and the forensic services had in 1996, but obviously there is a significant sea-change as far as examining these articles is concerned now.

“That would get us minuscule elements of identification we were unable to get 20 or even 10 years ago.”

He added: “This case is not going away for the police.

“It is one of our top priorities and is never far away from the forefront of our thoughts.”

Police Scotland will also be staging a media event in Bonhill on Monday to raise the profile of the unsolved case once again.

Caroline, 14, had left her home in Bonhill and was walking towards her boyfriend’s house in Renton when she was violently attacked.

The schoolgirl’s body was found partially in the water near to the Black Bridge in a case that horrified Scotland.

Caroline’s mum Margaret McKeitch has battled for justice over the past two decades.

Earlier this year Margaret told the Lennox Herald she would not find closure until her daughter’s killer was brought to justice.

She said: “I thought that by this time someone would have been caught and made to pay for what they did.

“Twenty years is a long time but to me it’s all still so fresh in my mind. It’s always there and always will be until they catch whoever is responsible. I need that closure. The pain isn’t any less but the hoping gets harder and harder to keep up.